Radiopaque electrical needle

ABSTRACT

A method and apparatus are disclosed for improving accuracy of placement of needles during delivery of high frequency signals near a neural structure to form lesions. The apparatus includes a needle that can deliver electrical current where a portion of the needle is electrically insulated and a portion of the needle is exposed and electrically active, thereby causing lesions. The needle includes radiopaque marking to differentiate the electrically insulated region from the exposed region, allowing it to be better discerned in the body under fluoroscopy.

TECHNICAL FIELD

[0001] The invention relates to a needle that delivers electrical current and more particularly to a needle that delivers high frequency electrical current in the vicinity of a neural structure.

BACKGROUND OF THE ART

[0002] A minimally invasive technique of delivering high frequency electrical current has shown to relieve localized pain in many patients. The high frequency electrical current is typically delivered from a generator via connected electrodes that are placed in a patient's body. The needles include an insulated shaft with an exposed electrically conductive tip. Tissue resistance to the high frequency electrical current at the tip causes heating of adjacent tissue. When temperature increases sufficiently tissue coagulates. The temperature that is sufficient to coagulate unmyelinated nerve structures is 45° C., at which point a lesion is formed and pain signals are blocked. This results in relief from pain.

[0003] Needles with varying geometries are used in such applications. For example, the exposed tip of the needle can be pointed, blunt and rounded or open, varying in shape in accordance with the needs of different procedures. Pointed tips are self-penetrating while rounded tips are useful in soft tissue areas such as the brain where it is critical not to damage nerves. However, blunt needles can do more tissue damage than small diameter sharp needles. Open tips can be used to deliver a therapeutic agent during electrical treatment. U.S. Pat. No. 6,146,380 to Racz et al. describes electrical needles with curved tips used in high frequency lesioning.

[0004] This technique of relieving back pain has also been used with needles penetrating the intervertebral disk. U.S. Pat. Nos. 5,433,739 and 5,571,147 to Sluijter et al. and WIPO publication WO 01/45579 to Finch et al. describe needles that are used in the intervertebral disk to relieve back pain caused by herniated disks.

[0005] For treatment, the needle having a hollow shaft and a removable stylet therein is inserted into the patient's body and positioned. Once the needle is positioned, the stylet is withdrawn and a distal end of a high frequency probe is inserted until the distal end of the probe is at least flush with the distal end of the shaft, (i.e. the exposed tip). The probe is connected to an external signal generator that generates high frequency electrical current.

[0006] These needles are often used to denervate certain portions of a spine of the patient. Accurate placement of the needle in a complicated structure like the spine requires great technical skill by a treating clinician. In these procedures, the needle is viewed via X-ray or a fluoroscope to assist placement and is guided into the body. One limitation of the technique used currently is that the insulated shaft is not distinguishable from the exposed tip of the needle under X-ray or fluoroscopy. Therefore, accurate visualization of the exposed tip is not possible.

[0007] Prior art devices for accurate placement have not been used in conjunction with radio frequency needles. Radiopaque marking has been used to accomplish precise placement of catheters and stents. U.S. Pat. No. 5,429,597 to Demello et al. discloses a balloon catheter having a radiopaque distal tip composed of a polymer mixed with a radiopaque powder such as tungsten. U.S. Pat. No. 6,315,790 to Gerberding et al. describes a catheter constructed with radiopaque polymer hubs where the hubs provided the dual function of stent crimping and marker bands.

[0008] An example of a catheter utilizing an external marker band is described in U.S. Pat. No. 5,759,174 to Fischell et al. The catheter has a single external metal marker band to identify the central portion of the stenosis once the delivery catheter is removed.

[0009] In spite of the improved illumination of the aforementioned devices when marked, there are some limitations to their application. Upon attachment conventional radiopaque markers may project from the surface of the catheter or stent, thereby causing a departure from its ideal profile. Some markers add rigidity to the stent and catheter in areas that had been designated for deformation. A needle for delivering radio frequency that overcomes some or all of the limitations of the prior art is desired.

SUMMARY OF THE INVENTION

[0010] The present invention provides for improved placement of a needle delivering high frequency energy by incorporating radiopaque markers to distinguish the exposed tip from the shaft under fluoroscopic visualization.

[0011] To facilitate precise placement of the exposed tip, the tip is distinguishable from the rest of the needle when viewed under X-rays and fluoroscopy. When a needle with radiopaque marking, according to the present invention, is inserted in the patient's body, the location of a lesion made or to be made by the needle can be easily determined, as the tip of the needle can be distinguished from the electrically insulated shaft.

[0012] The present invention provides a needle for insertion into a patient's body comprising an electrically insulated shaft having an electrically conductive tip portion and a radiopaque marker associated with at least one of the shaft and the tip portion.

[0013] The tip portion of the needle is the exposed tip and can be of varying dimensions. The radiopaque marker distinguishes the electrically insulated portion of the needle from the tip portion. This effectively identifies the position of the needle when in the body. The marker may be adapted to needles having various geometric shapes. The insulated portion of the needle may include an insulating coating. The coating may cover the radiopaque marker on the needle preventing a departure from the needle's true profile.

[0014] The radiopaque marker can comprise bands or radiopaque coatings of metals/polymers, or radiopaque materials deposited on the surface of the needle by techniques such as ion implantation or vapor deposition. These features and others will be apparent in the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order that the invention may be readily understood, embodiments of the invention are illustrated by way of examples in the accompanying drawings, in which:

[0016]FIG. 1 is a schematic illustration of a needle connected to a high frequency generator, in accordance with the present invention;

[0017]FIG. 2 is a side elevation view of an embodiment of the needle of the present invention, including a stylet;

[0018] FIGS. 3 to 7 illustrate side elevation views of different embodiments of the needle in accordance with the present invention, with radiopaque marking; and

[0019]FIG. 8 illustrates a stylet according to the present invention including radiopaque marking.

DETAILED DESCRIPTION OF THE INVENTION

[0020] In accordance with an aspect of the invention a medical apparatus is provided for delivering high frequency electrical current to neural structures. As illustrated in FIG. 1, the medical apparatus comprises a generator 100 for producing high frequency electrical current, a needle 102 with an electrical probe 110 connected to the generator 100 that is placed in the needle 102 for delivering the high frequency electrical current and a reference electrode 101 that completes the circuit. The needle 102 with the probe 110 is placed in a portion of a patient's body indicated generally at 106.

[0021] As can be seen more clearly in FIG. 2, the hollow shaft of the needle 102 is covered with an insulating coating 103 leaving a portion of the tip 104 uncoated, exposed and electrically conductive. The tip 104 may have a sharpened end that will assist with penetration of the tip 104 into the tissue of the body 106 during percutaneous entry. The exposed tip 104 represents the active electrode area. The reference electrode 101 typically has a much larger area than the exposed tip 104 so that there is no heating at the surface of the body 106 where the reference electrode 101 is attached. The passage of high frequency electrical current through the needle 102 produces a lesion 105 in the region of the exposed tip 104. The lesion 105 causes coagulation of the neural structures in that region and is responsible for pain relief. It is therefore important to know the position of the exposed tip 104 to gauge the relative position and region that will be affected by the high frequency electrical current.

[0022] As stated above, FIG. 2 depicts the needle 102 having a hollow shaft typically of one or more metals and a hub 201. Preferably the hub 201 is a Luer lock type molded to the shaft; however, other methods of attachment may be used as will be understood by a person skilled in the art. Insulated in needle 102 through the hollow shaft is an elongate stylet 205 shown in dotted outline. The stylet 205 is adapted to assist in piercing the skin and tissue for entry to a treatment area. The stylet 205 comprises a cap 200 cooperating with Luer lock hub 201. The hub 201 is also operable to accommodate an electrical probe 110 that is inserted into the shaft of the needle 102 when the stylet 205 is removed. A portion of the shaft is covered with an electrically insulating coating 103 leaving the tip 104 exposed. The end-point of the insulating coating 103 on the needle 102 is indicated at numeral 204. In use, the needle 102 with the stylet 205 is inserted into the body 106. Once a correct position has been attained the stylet 205 is removed and the electrical probe 110 that delivers the high frequency electrical current is inserted through the needle 102.

[0023] The needle 102 with the stylet 205 is inserted into the patient's body 106 under X-ray/fluoroscopic guidance. One common method for inserting the needle 102 is to locate an X-ray source along one or more desired axes. An image detector on the opposite side of the body portion 106 where the needle 102 is inserted receives the X-rays, thereby permitting verification of the proper location and orientation of the tip 104. Radiopaque marking on the needle 102 or stylet 205 will enable its better visualization in this process. A radiopaque marker could be applied on selected portions of the needle 102 by, for example, use of masks. Advantageously selected patterns of radiopacity will allow the precise orientation to be discerned by inspection of the fluoroscopic image. FIGS. 3 to 8 illustrate different exemplary embodiments of patterns of radiopacity that can be adopted in this invention. It will be understood by persons skilled in the art that other shapes and patterns may be adopted.

[0024] In the embodiment illustrated in FIG. 3 a radiopaque band 300 is located at the edge 204 of the coating and thereby aids in distinguishing between the coated region 103 and uncoated region 104. The radiopaque band 300 may be located before the coating end-point 204 or just after the coating end point 204. It may run 360° around the shaft or be applied through a certain distance of the circumference, for example through 180° or 90°. FIG. 3 illustrates one embodiment that includes a radiopaque band 300 through 180° of the shaft, on the side of the beveled tip, just before the coating end-point 204. This provides a clear demarcation between the coated 103 and exposed regions 104 of the needle 102.

[0025] The band 300 can be applied in a number of ways including techniques such as, but not limited to, vapor deposition, ion implantation, dip coating, metal plating and electro plating. Bands of radiopaque materials such as platinum iridium bands can also be fused onto the needle 102.

[0026] An alternate embodiment of the invention is depicted in FIG. 4. A radiopaque marker 400 may be placed on the needle 102 to distinguish between the coated metal shaft 103 and the exposed metal tip 104 and may be a variety of shapes and sizes. The shape of the marker 400 may also be used to indicate the direction of the beveled tip.

[0027]FIG. 5 illustrates another embodiment of the invention. The entire exposed part 104 of the needle 102, is radiopaque indicated at numeral 500 and can be discerned better when viewed under a fluoroscope. The coated region of the needle 103 can be masked and the exposed tip 104 coated with a radiopaque material. Techniques such as vapor deposition and ion bombardment can be used to achieve such coating.

[0028] An alternate embodiment of this invention can be obtained by imparting radiopacity to the insulating coating 600 as illustrated in FIG. 6. The insulating coating on the needle can be made radiopaque in a number of ways such as vapor deposition, ion-bombardment and ion-implantation. This renders the entire insulated portion of the needle radiopaque.

[0029]FIG. 7 illustrates the needle 102 with two radiopaque bands 700 at the coating end-point 204 and the edge of the exposed tip 104. This defines the region of the exposed tip 104 where delivery of high frequency electrical current to the tissue 106 occurs.

[0030]FIG. 8 illustrates the stylet 205 with radiopaque marking 800, which may include any of the embodiments described in FIGS. 3-7 above. The stylet 205 and needle 102 are inserted into the patient's body 106 to ensure correct placement. The radiopacity on the stylet 205 will serve to identify the exposed tip 104 on the needle 102.

[0031] An example of suitable material that may be used to impart the desired radiopacity is radiopaque ink with tungsten that is pad printed. The material is selected based on its radiopacity. Other suitable materials include, but are not limited to, high-density metals such as platinum, iridium, gold, silver, tantalum or their alloys, or radiopaque polymeric compounds. Such materials are highly visible under fluoroscopic illumination and are therefore visible even at minimal thickness.

[0032] The embodiments of the invention described above are intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims. 

We claim:
 1. A needle for insertion into a patient's body comprising: an electrically insulated shaft having an electrically conductive tip portion; and a radiopaque marker associated with at least one of the shaft and the tip portion.
 2. The needle of claim 1, wherein the radiopaque marker is located on at least a portion of the periphery of the shaft.
 3. The needle of claim 1, wherein the radiopaque marker is band-shaped.
 4. The needle of claim 1, wherein the shaft comprises an insulating coating.
 5. The needle of claim 4, where the insulating coating covers the radiopaque marker.
 6. The needle of claim 4, wherein the insulating coating is radiopaque.
 7. The needle of claim 1, wherein the needle is operable to connect to an energy source.
 8. The needle of claim 7, wherein the needle is operable to deliver high frequency electrical current.
 9. The needle of claim 1, wherein the tip portion is beveled and the radiopaque marker is shaped to indicate the direction of the tip.
 10. The needle of claim 1, wherein the radiopaque marker comprises at least two bands defining the tip portion.
 11. The needle of claim 1, wherein the tip portion is radiopaque.
 12. The needle of claim 1, wherein the insulated shaft is radiopaque.
 13. The needle of claim 1 comprising a stylet and wherein the shaft is hollow for receiving the stylet and wherein the radiopaque marker is associated with at least one of the shaft, the tip portion and the stylet.
 14. A needle for insertion into a patient's body comprising: an electrically insulated hollow shaft having an electrically conductive tip portion; and a stylet having a radiopaque marker, the stylet operable to be located in the needle during insertion and operable to be removed therefrom after insertion.
 15. An apparatus for delivering high frequency electrical current to neural structures comprising: an energy source for supplying high frequency electrical current; a needle connected to the energy source comprising an electrically insulated shaft having an electrically conductive tip portion located at one end of the shaft and a radiopaque marker associated with at least one of the shaft and the tip portion; and at least one reference electrode for completing the electrical circuit.
 16. A method for positioning a needle for delivering high frequency electrical current to neural structures comprising the steps of: (i) providing a needle operable for connection to an energy source, said needle comprising an electrically insulated shaft having an electrically conductive tip portion located at one end of the shaft and a radiopaque marker associated with at least one of the shaft and the tip portion; (ii) positioning the needle to a location to treat the neural structure; and (iii) verifying the position of the needle using the radiopaque marker.
 17. The method of claim 16 comprising: (iv) delivering high frequency electrical current through the needle to the neural structure.
 18. The method of claim 16, wherein the needle comprises a stylet received within the shaft and the radiopaque marker is associated with at least one of the shaft the tip portion and the stylet.
 19. The method of claim 18 comprising removing the stylet prior to delivering high frequency electrical current.
 20. The method of claim 19 comprising inserting an electrical probe into the needle and delivering high frequency electrical current via the electrical probe. 